Memory including a selector switch on a variable resistance memory cell

ABSTRACT

Embodiments include but are not limited to apparatuses and systems including memory having a memory cell including a variable resistance memory layer, and a selector switch in direct contact with the memory cell, and configured to facilitate access to the memory cell. Other embodiments may be described and claimed.

RELATED APPLICATION

The present application is a direct national filing claiming priority toInternational Patent Application No. PCT/IT2009/000537, which was filedon 30 Nov. 2009, titled “MEMORY INCLUDING A SELECTOR SWITCH ON AVARIABLE RESISTANCE MEMORY CELL,” the entire disclosure of which ishereby incorporated by reference.

BACKGROUND

Memory devices including variable resistance memory cells may representa low-cost alternative for future high-density memories. Variableresistance memory cells such as organic-based memory and phase changememory sometimes may be implemented in crossbar architectures, whereinmore than one memory array is integrated in a three-dimensional stackedmemory chip.

BRIEF DESCRIPTION OF THE DRAWINGS

Subject matter is particularly pointed out and distinctly claimed in theconcluding portion of the specification. The foregoing and otherfeatures of the present disclosure will become more fully apparent fromthe following description and appended claims, taken in conjunction withthe accompanying drawings. Understanding that these drawings depict onlyseveral embodiments in accordance with the disclosure and are,therefore, not to be considered limiting of its scope, the disclosurewill be described with additional specificity and detail through use ofthe accompanying drawings, in which:

FIG. 1 illustrates an example apparatus comprising a memory cellincluding a variable resistance memory layer, and a selector switch indirect contact with the memory cell;

FIGS. 2 and 3 are schematic representations of a portion of an examplememory array architecture including memory cells including a variableresistance memory layer, and a selector switch in direct contact withthe memory cell;

FIG. 4 illustrates an example memory cell including a variableresistance memory layer, and a selector switch in direct contact withthe memory cell;

FIG. 5 illustrates another example memory cell including a variableresistance memory layer, and a selector switch in direct contact withthe memory cell;

FIG. 6 illustrates an example memory cell including a variableresistance memory layer, and a selector switch in direct contact withthe memory cell;

FIG. 7 is a flow diagram illustrating some of the operations associatedwith an example method of making an apparatus comprising a memory cellincluding a variable resistance memory layer, and a selector switch indirect contact with the memory cell; and

FIG. 8 is a block diagram of an example system including an apparatuscomprising a memory cell including a variable resistance memory layer,and a selector switch in direct contact with the memory cell;

all arranged in accordance with various embodiments of the presentdisclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented herein. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe Figures, can be arranged, substituted, combined, separated, anddesigned in a wide variety of different configurations, all of which areexplicitly contemplated herein.

This disclosure is generally drawn, inter alia, to memory having amemory cell including a variable resistance memory layer, and a selectorswitch in direct contact with the memory cell, and configured tofacilitate access to the memory cell. Embodiments include, but are notlimited to, methods, apparatuses, and systems. Other embodiments mayalso be disclosed and claimed.

The present disclosure recognizes that variable resistance memory cellssuch as molecular memory and phase change memory sometimes tend to havelower thermal thresholds relative to traditional three-terminaltransistor-based memory cells. For instance, in some cases, exposure totemperatures over 200-300° C. may have a detrimental impact on thefunctionality of variable resistance memory cells. The presentdisclosure further recognizes that silicon-based selectors for decodingthese memory arrays may be incompatible with variable resistance memorycells at least for embodiments in which variable resistance memory cellsare implemented in crossbar architectures, wherein more than one memoryarray is integrated in a three-dimensional stacked memory chip. Thisincompatibility may be due at least in part to the fabricationtemperature of silicon-based selectors commonly being higher than thethermal threshold of various types of variable resistance memory.

The present disclosure is drawn to a memory cell including a variableresistance memory layer, and a selector switch in direct contact withthe memory cell. In various embodiments in accordance with the presentdisclosure, the selector switch may be realized with a total thermalbudget that is compatible with the characteristics of the variableresistance memory layer. At least in some embodiments, for instance, theselector switch may be realized with a total thermal budget of less than150° C.

FIG. 1 illustrates an example apparatus 100 comprising a memory cell102, and a selector switch 104 configured to facilitate access to thememory cell 102, arranged in accordance with at least some embodimentsof the present disclosure. The memory cell 102 may comprise at least onelayer of variable resistance memory material, and the selector switch104 may be in direct contact with the memory cell 102 as illustrated. Invarious embodiments, the selector switch 104 may comprise a Schottkydiode.

The variable resistance memory material of the memory cells 102 maycomprise any variable resistance material suitable for the application.In various embodiments, the memory cell 102 comprising such variableresistance memory material may effectively function as programmableresistors, whose resistance is variable based at least in part on avoltage applied (e.g., by a bit line and a word line) between theterminals of the memory cell 102.

In various embodiments, the variable resistance memory material maycomprise an organic switch material. Example organic switch material mayinclude a self assembled mono-layer, an organic-metal-organic complex,or bulk organic semiconductor realized with single molecules, oligomers,or polymers. Example organic switch material may include a polymer suchas porphyrin polymer, polyacetylene, polypyridine, poly styrene,polyaniline, polythiphene, polypyrrole, polysilane, or the like. Invarious embodiments, the organic switch material may include aconductive material such as silver or copper dispersed therein.

In various embodiments, the variable resistance memory material maycomprise a phase change material. A phase change material may include achalcogenide comprising an alloy containing a group VI element (e.g.,oxygen, sulfur, selenium, tellurium, etc.), also known as chalcogens,combined with a group IV/V element (e.g., germanium, tin, arsenic,antimony, etc.). An example chalcogenide may include Ge₂Sb₂Te₅ (GST).

Other variable resistance memory material may be similarly suitable.Resistive random access memory, for example, may enlist a transitionmetal oxide or other suitable variable resistance material.

In various embodiments, the apparatus 100 may be a memory devicecomprising a memory array including the memory cell 102 and a pluralityof other similarly configured memory cells. In various ones of theseembodiments, the memory cell 102 may be coupled to one or more othersimilarly configured memory cells by a word line 106 and a bit line 108,as discussed more fully herein. The apparatus 100 may include variousother elements for forming the memory device including, for example, oneor more dielectric layers 110, one or more sealing layers 112, and/orone or more conductive plugs 114. The one or more conductive plugs 114may be configured to allow electrical access to the memory cell 102 byway of the selector switch 104, and so, may comprise a conductivematerial such as tungsten or the like. The one or more conductive plugs114 may include a diffusion barrier layer 116 formed between the one ormore conductive plugs 114 and various surrounding elements such as thedielectric layer 110.

FIGS. 2 and 3 are schematic representations of a portion of an examplememory array architecture including memory cells 102 including avariable resistance memory layer, and a selector switch 104 in directcontact with the memory cell 102, arranged in accordance with at leastsome embodiments of the present disclosure. As illustrated, thearchitecture may include a plurality of word lines 106 and a pluralityof bit lines 108. The plurality of memory cells 102 may be arranged inan array of a plurality of columns and a plurality of rows. Each memorycell 102 in a column may be coupled to each other by a corresponding bitline 108, and each memory cell 102 in a row may be coupled to each otherby a corresponding word line 106.

As illustrated, a selector switch 104 may be provided in direct contactwith each of the plurality of memory cells 102. In various embodiments,the plurality of memory cells 102 and selector switches 104 may besuccessively stacked to form a three-dimensional crossbar memory arrayin which the plurality of memory cells 102 and the selector switches 104may be located at intersecting junctions of the bit lines 108 and wordlines 106. It should be noted that although the illustrated embodimentdepicts three layers of memory cells 102, memory arrays within the scopeof the present disclosure may include fewer or more than three layers.

FIGS. 4-6 illustrate various examples of the memory cell 102 andselector switch 104, arranged in accordance with at least someembodiments of the present disclosure.

The memory cell 102 may include any one or more layers suitable forforming a memory cell. In various embodiments, the memory cell 102 mayinclude a top electrode layer 118 and a bottom electrode layer 120, withthe variable resistance memory layer 122 disposed between the topelectrode layer 118 and the bottom electrode layer 120. In various onesof these embodiments, the selector switch 104 may be in direct contactwith the top electrode layer 118 of the memory cell 102.

The top electrode layer 118 and the bottom electrode layer 120 maycomprise any suitable conductive material. Example suitable conductivematerials may include aluminum, titanium, carbon, nickel, gold, silver,platinum, or a combination of one or more thereof. Other conductivematerials may be similarly suitable.

As noted herein, the selector switch 104 may be a Schottky diode.Accordingly, various embodiments of the selector switch 104 may beconfigured in a manner suitable for realizing a Schottky diode structureincluding a semiconductor-metal junction. In various embodiments, and asillustrated in FIG. 4, the selector switch 104 may include anon-silicon-based semiconductor layer 124 and a metal layer 126. Thesemiconductor layer 124 may comprise any suitable non-silicon-basedsemiconductor including, for one or more doped layers. In variousembodiments, the non-silicon-based semiconductor layer 124 may comprisen-type doped zinc oxide.

The metal layer 126 may similarly comprise any suitable material forforming the Schottky diode structure in conjunction with the selectednon-silicon-based semiconductor layer 124. In various embodiments, forexample, the metal layer 126 may comprise silver. Other metals may besimilarly suitable, including, for example, aluminum, platinum, silver,carbon, titanium, nickel, or gold, or combinations thereof.

The selector switch 104 may include one or more additionalnon-silicon-based semiconductor layers 124. As illustrated in FIG. 5,for example, the non-silicon-based semiconductor layers 124 may comprisetwo non-silicon-based semiconductor layers 130, 132. Thenon-silicon-based semiconductor layers 130, 132 may comprise anysuitable combination of materials for forming the Schottky diodestructure. In various embodiments, for example, one of thenon-silicon-based semiconductor layers 130, 132 may comprise n-typedoped zinc oxide, while the other one of the non-silicon-basedsemiconductor layers 130, 132 may comprise p-type doped zinc oxide.

The selector switch 104 may include one or more additionalnon-silicon-based semiconductor layers 124 and/or one or more additionalmetal layers 126. As illustrated in FIG. 5, for example, the selectorswitch 104 may include another metal layer 128. The other metal layer128 may comprise the same or different metal than that of the metallayer 126. In some embodiments, for example, the metal layer 126comprises silver, while the metal layer 128 comprises a titanium/goldalloy.

In various embodiments, the memory cell 102 and the selector switch 104may be reversed relative to the embodiment illustrated in FIG. 1. Asillustrated in FIG. 6, for example, the memory cell 102 may be formed onthe selector switch 104.

The apparatuses of FIGS. 1-6 may be more clearly understood withreference to FIG. 7. FIG. 7 is a flow diagram illustrating some of theoperations associated with an example method of making an apparatuscomprising a memory cell including a variable resistance memory layer,and a selector switch in direct contact with the memory cell, arrangedin accordance with at least some embodiments of the present disclosure.It should be noted that although the method is illustrated as a seriesof sequential steps, the method is not necessarily order dependent.Moreover, methods within the scope of this disclosure may include moreor fewer steps than that illustrated.

Turning now to FIG. 7, with continued reference to various elements ofthe apparatuses of FIGS. 1-6, the method 700 may include one or morefunctions, operations, or actions as is illustrated by block 702 and/orblock 704. Processing for the method 700 may start with block 702, “Forma memory cell including a variable resistance memory layer.” Forming thememory cell may include forming a bottom electrode layer, the variableresistance memory layer on the bottom electrode layer, and a topelectrode layer on the variable resistance layer. The variableresistance memory layer may comprise a molecular switch material or aphase change material.

In various embodiments, forming the memory cell may include forming aplurality of memory cells arranged in an array of a plurality of columnsand a plurality of rows, and forming a plurality of bit lines and aplurality of word lines, wherein each memory cell in a column is coupledto each other by a corresponding bit line, and wherein each memory cellin a row is coupled to each other by a corresponding word line.

From block 702, the method 700 may proceed to block 704, “Form aselector switch in direct contact with the memory cell.” Forming theselector switch may include forming the selector switch with a totalthermal budget of less than 150° C.

Embodiments of apparatuses described herein may be incorporated intovarious other apparatuses and systems, including but are not limited tovarious computing and/or consumer electronic devices/appliances, such asdesktop or laptop computers, servers, set-top boxes, digital reorders,game consoles, personal digital assistants, mobile phones, digital mediaplayers, and digital cameras. A block diagram of an example system 800is illustrated in FIG. 8. As illustrated, the system 800 may include amemory device 802. In various embodiments, memory device 802 may be avolatile or a non-volatile memory device. In various embodiments, memorydevice 802 may be a NAND, NOR, or phase change non-volatile flash memorydevice. In various embodiments, the memory device 802 may at least onememory cell including a variable resistance memory layer, and a selectorswitch in direct contact with the memory cell, collectively 804. Theselector switch may be configured to selectively couple the at least onememory cell to an output terminal 816 of the memory device 802.

In various embodiments, memory device 802 may be operatively coupled toa host logic device 806. In various embodiments, the host logic device806 may be mounted to the same substrate memory device 802 is mounted.In other embodiments, memory device 802 may be joined with host logicdevice 806. In various embodiments, the host logic device 806 may be amicrocontroller, a digital signal processor or a general purposemicroprocessor. In various embodiments, host logic device 806 mayinclude a processor core 808, or a plurality of processor cores 808.

In various embodiments, the system 800 may further comprise a host logicdevice bus 810 operatively coupling the memory device 802 and the hostlogic device bus 810, including electrically coupling memory device 802and the host logic device 806. In various embodiments, host logic devicebus 810 may be disposed on a substrate to which both memory 802 and hostlogic device 806 are mounted.

In various embodiments, the system 800 may further includecommunications interface(s) 814 to provide an interface for system 800to communicate over one or more networks and/or with any other suitabledevice. Communications interface(s) 814 may include any suitablehardware and/or firmware. Communications interface(s) 814 for oneembodiment may include, for example, a network adapter, a wirelessnetwork adapter, a telephone modem, and/or a wireless modem. Forwireless communications, communications interface(s) 814 for oneembodiment may use one or more antennas (not illustrated).

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art may translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

Various operations may be described as multiple discrete operations inturn, in a manner that may be helpful in understanding embodiments;however, the order of description should not be construed to imply thatthese operations are order-dependent. Also, embodiments may have feweroperations than described. A description of multiple discrete operationsshould not be construed to imply that all operations are necessary.Also, embodiments may have fewer operations than described. Adescription of multiple discrete operations should not be construed toimply that all operations are necessary.

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, such as in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as “up to,” “at least,” “greater than,” “less than,” and the likeinclude the number recited and refer to ranges which can be subsequentlybroken down into subranges as discussed above. Finally, as will beunderstood by one skilled in the art, a range includes each individualmember.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

What is claimed is:
 1. A method comprising: forming a memory cellincluding a variable resistance memory layer disposed between electrodelayers, wherein the electrode layers are carbon layers; forming asemiconductor-oxide-based, non-silicon selector switch in direct contactwith the memory cell at a temperature of less than 150° C.; providing asealing layer in contact with the memory cell and thesemiconductor-oxide-based, non-silicon selector switch; providing aplurality of dielectric layers at least partially surrounding the memorycell, the semiconductor-oxide-based, non-silicon selector switch, andthe at least one sealing layer, the plurality of dielectric layers indirect contact with at least the memory cell and the at least onesealing layer, wherein the sealing layer separates two adjacentdielectric layers of the plurality of dielectric layers; providing afirst conductive plug on the at least one sealing layer, the firstconductive plug configured to allow electrical access between thesemiconductor-oxide-based, non-silicon selector switch and a word line;providing a first diffusion barrier layer at least partially surroundingthe first conductive plug; providing a second conductive plug on thememory cell, the second conductive plug configured to allow electricalaccess between the memory cell and a bit line; and providing a seconddiffusion barrier layer at least partially surrounding the secondconductive plug.
 2. The method of claim 1, wherein the forming thesemiconductor-oxide-based selector switch comprises: forming a zincoxide layer on the memory cell; and forming a contact layer on the zincoxide layer; wherein the contact layer comprises silver, platinum,carbon, aluminum, titanium, or nickel.
 3. The method of claim 1, whereinforming the memory cell comprises: forming a plurality of memory cellsarranged in an array of a plurality of columns and a plurality of rows;forming a plurality of bit lines and a plurality of word lines, whereineach memory cell in a column is coupled to each other by a correspondingbit line, and wherein each memory cell in a row is coupled to each otherby a corresponding word line.
 4. The method of claim 1, wherein thesemiconductor-oxide-based, non-silicon selector switch comprises asemiconductor oxide having a deposition temperature below a meltingtemperature of the variable resistance memory layer.
 5. The method ofclaim 1, wherein the semiconductor-oxide-based, non-silicon selectorswitch comprises a zinc oxide layer.
 6. The method of claim 5, whereinthe semiconductor-oxide-based, non-silicon selector switch furthercomprises a contact layer on the zinc oxide layer, and wherein the zincoxide layer is disposed between the contact layer and the memory cell,and wherein the contact layer comprises silver, platinum, carbon,aluminum, titanium, or nickel.
 7. The method of claim 1, wherein theselector switch comprises a p-type zinc oxide layer and an n-type zincoxide layer, and wherein the selector switch further comprises a firstcontact layer and a second contact layer, and wherein the p-type zincoxide layer and the n-type zinc oxide layer are disposed between thefirst contact layer and the second contact layer.
 8. The method of claim7, wherein at least one of the first contact layer and the secondcontact layer comprises silver, platinum, carbon, aluminum, titanium,nickel, gold, or aluminum.
 9. The method of claim 8, wherein the firstcontact layer comprises silver and the second contact layer comprises atitanium/gold alloy.
 10. The method of claim 1, wherein the variableresistance memory layer comprises an organic material selected from thegroup including a self assembled mono-layer, an organic-metal-organiccomplex, or bulk organic semiconductor having single molecules,oligomers, or polymers.
 11. The method of claim 1, wherein the variableresistance memory layer comprises a chalcogenide.
 12. The method ofclaim 1, wherein the formed memory cell is part of a plurality of memorycells arranged in an array of a plurality of columns and a plurality ofrows, wherein the apparatus further comprises a plurality of bit linesand a plurality of word lines, wherein each memory cell in a column iscoupled to each other by a corresponding bit line, and wherein eachmemory cell in a row is coupled to each other by a corresponding wordline.
 13. The method of claim 12, wherein the plurality of memory cellsand the at least one selector switch form a crossbar memory array. 14.The method of claim 1, wherein the selector switch is configured toselectively couple the memory cell to an output terminal of the memorydevice.
 15. A memory cell formed from the method of claim
 1. 16. A flashmemory device comprising the memory cell of claim
 15. 17. The method ofclaim 1, wherein the first and second conductive plugs comprisetungsten.